The present invention relates to an expandable implant capable of providing inter-bone stabilization (e.g., intervertebral spinal stabilization) and also capable of extruding materials, such as osteogenic material, upon expansion. The present invention also relates to a method of stabilizing bones (e.g., spinal vertebrae) with respect to one another while extruding osteogenic material.
There are several situations where it becomes desirable to stabilize one bone with respect to another. One exemplary situation arises in patient's who suffer from chronic low back pain. Chronic low back pain is one of the most common and perplexing problems facing the field of orthopedic surgery. In addition to patient discomfort, chronic low back pain has several adverse societal impacts, including lost income and possible chronic dependence on drugs, alcohol and public relief programs.
In many cases, low back pain can be avoided by preventing relative motion between spinal vertebrae. This treatment is commonly referred to as intervertebral stabilization. To abate low back pain, stabilization is directed to stabilizing contiguous vertebrae in the lumbar region of the spine.
Surgical techniques are known for use in spinal stabilization. These techniques seek to rigidly join vertebrae which are separated by a degenerative disk. Ideally, the surgery effectively replaces the vertebra-disk-vertebra combination with a single rigid vertebra. Various surgical techniques have been developed which attempt to approach or approximate this ideal.
One technique known in the art is to partially remove a degenerated disk and insert a bone graft into the void formed by the removed disk. Other techniques involve use of a surgical prosthetic implant which, acting alone or in combination with bone fragments, replaces the use of bone grafts. Such implants have been provided in the form of an implant that is placed between two adjacent vertebrae. The implant may contain bone fragments to facilitate bone growth. The implant contacts adjacent vertebral plates and achieves vertebral fusion after a sufficient amount of bone growth occurs, thus treating or preventing back pain in patients that have discogenic pain.
While conventional implants can be filled with bone fragments to expedite bone growth, it is believed that the mere presence of the bone fragments is not enough to achieve the rate of bone growth that would be provided if the bone fragments or other osteogenic material were extruded from the implant. There is consequently a need for an expandable implant which is adapted to extrude osteogenic material during its expansion and which thereby is adapted to expedite the bone growth and fusion process. By expediting the bone growth and fusion process, it is possible to reduce the amount of time between surgery and the patient's ability to return to work or perform physically demanding activities.
There also is a need for an expandable implant which can be repositioned in the event that the stabilization provided by the initial positioning of the implant creates an undesirable vertebral alignment.